I bemoaned Glock for years for not releasing a single stack 9mm pistol that is very concealable and can even fit in some pockets. Then, before Glock responded to those wanting another CCW choice, I decided to purchase a Kahr CW9, and I'm glad I did (and I'm a Glock fanboy). The CW9, at least the one I have, is reliable and accurate. Here's the dimensional comparison.
Kahr CW9
Caliber: 9mm
Capacity: 7+1
Operation: Trigger cocking DAO; lock breech; "Browning - type" recoil lug; passive striker block; no magazine disconnect
Barrel: 3.565", conventional rifling; 1-10 right-hand twist
Length O/A: 5.9"
Height: 4.5"
Slide Width: .90"
Weight: Pistol 15.8 ounces, Magazine 1.9 ounces
Grips: Textured polymer
Sights: Drift adjustable white bar-dot combat rear sight, pinned in polymer front sight
Finish: Black polymer frame, matte stainless steel slide
Glock 43
Caliber: 9mm
Capacity: 6+1
Operation: Safe Action Striker Fired-5.5lb
Barrel Length: 3.39"
Length O/A: 6.26in
Height: 4.25"
Slide Width: 1.02"
Weight: 17.95 ounces
Grips:
Sights: Bar dot?
Finish: Polymer frame/Tenifer coated steel slide
Glock ships with 2 mags and Kahr CW9 ships with one, advantage Glock.
MSRP: CW9 - $449 but can be purchased between $300-$350; Glock 43 - $589; advantage Kahr. (Add about $35 to the cost of the Kahr for an additional magazine.)
Overall, the Kahr barrel is a little longer than the Glock but the overall slide length is a little shorter; advantage Kahr.
Slide width: Slight advantage to Kahr.
Weight: Slight advantage to Kahr.
So it depends on which you prefer, a longer but smooth trigger pull of the Kahr, or the 5.5lb (in reality more like 7.5 lb) trigger pull of the striker fired Glock. Advantage: personal
Modularity: Advantage Glock
So without having fired, or even seen the Glock 43 in person, (after all, a Glock's a Glock) there's the comparison of the two pistols.